1. Technical Field
The present invention relates to a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving object.
2. Related Art
As an oscillator having high-accuracy oscillation characteristics on along-term basis, an atomic oscillator that oscillates based on energy transition of alkali metal atoms such as rubidium or cesium is known.
In general, the operation principle of an atomic oscillator is classified into two types including: a type in which a double resonance phenomenon caused by light and microwaves is used; and a type in which a quantum interference effect (CPT: Coherent Population Trapping) caused by two kinds of light having different wavelengths is used. As compared to an atomic oscillator in which the double resonance phenomenon is used, an atomic oscillator in which the quantum interference effect is used can be further reduced in size and thus has been expected to be mounted in various apparatuses in recent years (for example, refer to JP-A-2013-125907).
For example as disclosed in JP-A-2013-125907, an atomic oscillator in which the quantum interference effect is used includes: a gas cell that encapsulates a gaseous alkali metal; a light source that emits resonance light for causing the alkali metal in the gas cell to resonate; and a light detector (light receiving portion) that detects resonance light having passed through the gas cell. In such an atomic oscillator, when a difference in frequency between two kinds of resonance light is a specific value, an electromagnetically induced transparency (EIT) phenomenon occurs in which both the two kinds of resonance light pass through the alkali metal in the gas cell without being absorbed. At this time, an EIT signal, which is a sharp signal generated during the EIT phenomenon, is detected by the light detector, and this detected EIT signal is used as a reference signal.
However, in the atomic oscillator disclosed in JP-A-2013-125907, constantly polarized resonance light is continuously irradiated, and thus the number of electrons in the alkali metal contributing to resonance decreases over time. Therefore, the electromagnetically induced transparency phenomenon is less likely to occur, and the intensity of the EIT signal is attenuated. Therefore, there is a problem in that the atomic oscillator cannot oscillate at a high-accuracy reference frequency.